Most people will experience low back pain (LBP) during their adult lives and more than 50% of the people who experience an episode of LBP will have a recurrence. Despite the high health care costs associated with managing this condition, no treatment has been found to be consistently effective in improving the often persistent symptoms and related disability, and more importantly, curtailing the recurrences. It has been suggested that the lack of support of any one treatment is the result of studies being conducted on heterogeneous groups of people with LBP, and a system for classifying people with LBP into more homogeneous groups is needed. Recently, a system of classifying people with LBP based on movement-system related impairments has been described and tested. The impairments used to classify LBP are related to the specific directions of movements and alignments consistently related to the person's symptoms during (1) a clinical examination, and (2) functional activities. The primary purpose of this proposal is to conduct a prospective, randomized, controlled clinical trial to determine if treatment directed by a person's specific impairment- based LBP classification is more effective than non-specific physical therapy care in improving short- and long-term outcomes in people with chronic LBP. The specific aims of this study are to determine the effect of classification- specific treatment versus non-specific treatment across an 18 month period on (1) impairments which include symptoms (intensity, frequency, duration, location, and recurrences), movement and alignment impairments on clinical examination tests, and kinematics of movement and alignment impairments with standardized clinical tests, (2) functional limitations measured with the Oswestry LBP questionnaire and the Baecke Habitual Activity questionnaire, and (3) disability measured with the SF-36 and number of LBP-related activity limitations days. Classification-specific treatment will emphasize (1) changing the person's use of movement and alignment impairments in functional activities, (2) exercise to alleviate impairments, and (3) education to understand how specific directions of movements and alignments contribute to symptoms. The non-specific physical therapy treatment will include general trunk strengthening, trunk and extremity flexibility, and education about body mechanics and guidelines for performance of functional activities. Prognostic factors also will be examined. The findings from this study have important implications with regard to decisions made about examination and treatment methods used in rehabilitation of people with LBP, an often persistent, recurrent and costly condition.